Vibration is the main source of noise in a brake system. Noise generally results from rust, distorted or loose components, and/or the wearing or weakening of an original part. As components weaken or become fatigued from the heat and stress generated in the brake system, they no longer fit properly. Any brake system component vibration will result in a very audible, irritating noise such as a squeal.
Check the items below to troubleshoot the source of noise issues.
Rotors, Wheel Bearings and Hubs
Check the following:
- Check for loose or improperly adjusted wheel bearings
- Be sure to clean rust/corrosion from hub contact surface
- Check mounting hubs for excessive runout
- Wash rotors thoroughly with soap and water and use a bristle brush to remove dust and grit from peaks and valleys on the rotor’s contact surface
Caliper Bracket & Hardware
Replace all anti-rattle clips, springs and pins which can lose their spring tempering due to the higher brake heat. Make sure guide pins are not binding or corroded which could prevent the brake caliper from releasing properly and instead drag on the brake rotor. Clean any rust from the caliper surfaces where the anti-rattle clips mount to allow free movement of pads.
It is also important to clean the face of the caliper piston and the surface of the caliper that touches the brake pads. Removing rust and corrosion from these surfaces will help ensure the pads are parallel to the rotor surface.
The proper use of chemicals on the back of brake pads is also important when preventing unwanted noise from your brake system.
Disc Pads with Shims Attached
When installing disc pads with constrained layer shims already attached to the disc pad plate, the technician should put a slight coat of Wagner Silicone Lubricant on the back of the shim. This will aid as an additional noise suppressant.
Technicians should NOT put any other chemical compound on the back of the shim. Compounds that are tacky might cause the shim to be pulled from the back of the disc pad plate.
Disc Pads with IMI™
Wagner® TQ® brake pads, with their patented IMI Sound Insulator design, require that NO chemical compounds (EMP, silicone lubricants, moly lube, etc.) be placed on the insulator area of the disc brake pads. Use of chemicals on the insulator may reduce the insulator's effectiveness.
Disc Pads without Shims Attached
When installing disc pads that do not have shims attached (as per OE) the technician should utilize the EMP compound that is included in the box with the pads. EMP compound should be put on the back of the disc pad plate where there is contact with the outer caliper fingers or caliper piston when installed.
One way to reduce the chance of vibration and/or noise is to perform the break-in process known as burnishing. This important step ensures that the brake pad is properly mated to the rotor. If the transfer of material is not done correctly, it can lead to vibration and/or noise. The typical break-in process involves:
- No panic stops
- Performing 20 slow-downs from 50mph to 20mph using light pedal pressure
- Allowing at least 30 seconds between each slow-down session
The content contained in this article is for entertainment and informational purposes only and should not be used in lieu of seeking professional advice from a certified technician or mechanic. We encourage you to consult with a certified technician or mechanic if you have specific questions or concerns relating to any of the topics covered herein. Under no circumstances will we be liable for any loss or damage caused by your reliance on any content.
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